In recent years, information provided to passengers and crew members who use mobile bodies such as trains tends to increase. It is desirable to apply a high-speed line suitable for a data capacity to a line for communicating this information data (hereinafter simply referred to as “line”). However, the increase in speed of the line often involves enormous investments of expenses, time, and the like for establishment of a communication system. Therefore, as means for solving the problem, a method such as multi-link for using a plurality of existing lines to expand a communication capacity as a whole is known. When lines of a wireless system are applied to a communication system, transmission rates of the lines dynamically change according to, for example, fluctuation in a peripheral environment of a mobile body. Therefore, the multi-link by the wireless system has a problem in that, in some case, actual transmission rates of the lines do not coincide with one another and band use efficiency of the entire lines falls.
In the past, a multi-link communication apparatus (hereinafter simply referred to as “communication apparatus”) described in Patent Literature 1 includes a monitoring unit that monitors effective transmission rates of wireless communication lines and a dividing unit that allocates, based on a monitoring result, data amounts corresponding to the effective transfer speeds of the lines to the lines. Data generated first in a communication apparatus on a transmission side is divided into data of fixed sizes corresponding to transmission rates of initial setting (referred to as “rated transmission rates”) in the lines by the dividing unit of the transmission side communication apparatus. The divided data (hereinafter referred to as “short data”) is transmitted to the lines by a transmitting and receiving unit. On the other hand, the actual transmission rates of the lines are monitored by the transmitting and receiving unit. The monitoring unit acquires the effective transmission rates of the lines from the transmitting and receiving unit every time the short data is transmitted to the lines. When transmission data is generated for the second or more time, the dividing unit divides this transmission data according to the effective transmission rates obtained by the monitoring unit. The communication apparatus in the past configured in this way realizes multi-link communication for keeping throughput of the entire lines high.